The project of Long Term Evolution was started by 3GPP in 2005, aiming to provide supports for increasing demands of operators and subscribers with a higher data throughput and an improved network performance.
Multimedia Broadcast/Multicast Service (MBMS), introduced by 3GPP Rel6, is a point-to-point service for transmitting data from one data source to a plurality of subscribers so as to share network (including core network and access network) resources and provide services to a possibly largest number of multimedia subscribers having identical demands at the expense of resources as less as possible. In a radio access network, MBMS service uses a common transmission channel and a common radio bearer to implement both lower-rate message-type multicast and broadcast in pure text and higher-rate multicast and broadcast of multimedia services, such as mobile phone having television function.
FIG. 1 schematically shows an example of a mobile communication network as WCDMA system. As shown in FIG. 1, a plurality of NodeBs, such as NodeBs 11, 12 and 13, are connected to a NodeB controller, such as RNC (Radio Network Controller) 10 in the mobile communication network. A single RNC 10 manages several NodeBs. Each of the NodeBs is connected with RNC via a wired transmission, and the interface between them is defined as Iub interface. RNC 10 may also be connected to SGSN (Serving Gateway Support Node) of a System Architecture Evolution network (CN) via Iu interface.
FIG. 2 schematically shows a diagram of MBMS network structure in 3GPP Rel6 version. Network cells supporting MBMS includes BM-SC (Broadcast/Multicast Service Center), GGSN (GPRS Gateway Support Node), SGSN, access network (UTRAN) comprising NodeB and RNC, and UE (User Equipment). BM-SC is an entrance for content providers and adapted for authorization, initiating MBMS bearer service in PLMN (Public Landline Mobile Communication Network) and transmitting MBMS data in accordance with a predefined schedule. RNC performs allocation and control of radio resources on the MBMS bearer service and transmits MBMS service data to the NodeB, which is responsible for transmitting efficiently MBMS service data and control signaling via air interface.
Specification of SAE/LTE was defined by 3GPP since Rel7 version. In order to simplify network architecture and reduce delay, SAE/LTE cancels RNC as a network cell. The functions of RNC are distributed into NodeB (eNodeB) and core network. The current SAE/LTE-based network architecture is flatter than that before evolution. The portion of radio access network is reduced from the original structure of two network nodes (NodeB+RNC) to a structure of a single network (enhance NodeB, also simplified as eNB). MBMS is called EMBMS (Evolved MBMS) in the SAE/LTE-based network architecture.
The current version of Specification defines only an architecture supporting unicast service in terms of system architecture evolved networks. No proposal is given to an architecture supporting MBMS in system architecture evolved networks. There is a need for a system architecture evolved network entity for supporting MBMS in System Architecture Evolution.